Electrically Detected Magnetic Resonance of MEH-PPV diodes

Abstract

AbstractIn this work electrically detected magnetic resonance (EDMR) is used to study the electronic properties of poly(2-methoxy-5-(2'-ethyl-hexoxy)-1,4-phenylene vinylene) (MEHPPV) diodes. Two kinds of MEH-PPV diodes were characterized. The first one was a bipolar light emitting diode whose structure was ITO/MEH-PPV/Al. In this diode the EDMR signal is composed of two lines, a line that can be fitted by a lorentzian with peak-to-peak linewidth of 5.0 ± 0.5 G and the other best fitted with gaussian line with a linewidth of 24 ± 1 G. The g factor of both components is 2.002 ± 0.001 and signals were only observed at forward bias. The second diode is a hole only device, with a structure ITO/MEH-PPV/Au, the EDMR signal in this case is dominated by a gaussian line with peak-to-peak linewidth of 5 ± 1 G and average g factor of 2.0014 ± 0.0002. In high forward bias (V > 30 volts at T = 130K) a second line could be observed with a linewidth of 10 ± 2 G and a g factor of 2.0012 ± 0.0004. The signal from both types of diodes is quenching, and tipically10-5 in amplitude. The EDMR signal is assigned to the spin-dependent fusion of two like-charged polarons. Our results indicate that the narrower component is coming from positive polarons while the broader to negative polarons.